In the Boltzmann approximation, i.e. at \(\theta =0\)  in Eqs. (REF ) and (), the QvdWM
is reduced to the classical vdWM
[1]},
\(P_i=\sum _{j}\left[\frac{n_iT}{1-n_jb_{ij}} - a_{ij}n_in_j\right]~.\) 
